Abstract
•Thermal safety hazard in an underground metro depot was revealed.•Fire behavior, smoke spread, and ceiling temperature were successively addressed.•Modified correlations accounting for the coupling effect of blockage and tunnel slope were proposed.
The current research investigated the coupling effect of blockage and tunnel slope on spreading characteristics of the fire smoke and ceiling temperature distribution in a metro depot with one closed end. A series of 1/15 reduced scale experiments and full-scale numerical simulations were conducted to capture the global fire characteristics. The investigation addressed and compared the effect of tunnel slope on the fire plume behavior and ceiling temperature distribution in both uphill and downhill situations. The presence of the blockage upstream of the fire was further investigated to highlight the heat accumulation between the closed end and fire, and the associated effect on the pool fire mass burning rate. Comparison has been made between the ceiling temperature distribution of when the tunnel slope increases in both uphill and downhill tunnels. The coupling effect of blockage and tunnel slope was analyzed in relation to the maximum and extent of high temperature area at tunnel ceiling. Two empirical correlations have also been proposed to predict the maximum temperature and upstream temperature attenuation in a metro depot, accounting for the influence of blockage and tunnel slope. Comparison among the measurements, predicted values, literature models and data exhibit relatively good agreement.